Apparatus for extruding metal



Oct. 4, 1938. cz.I s. FARMER ET A1. 2,131,799

APPARATUS FOR EXTRUDING METAL FiledNov, 5, 1957 s sheets-sheet 1 CHAR/E5 JAMES en veqnd Thon/as JAMes Fo/eF/:Lp

Oct. 4, 1938.

Filed Nov. 5, 1957 Fig. 2.

5 Sheets-Sheet 2 W MIA/l MU f EP A T m/Q/VEYS Oct. 4, 1938. c. s. FARMERET AL 2,131,799

APPARATUS FOR EXTRUDING METAL Filed Nov, 5, 1937 5 Sheets-Sheet 3 VVE/V7' ORS Camus-s; Samnaun Fnkneeceased 5y @mlm Fen/vers Hmmm Emu/n',

CHHeLe-spT/msa 18E/Ime; anw" Wassmss Hfer/:Lp

wmp/mas Oct. 4, 1938. c. .s. FARMER`Er An. A 21,131,799

APPARATUS FOR EXTRUDING METAL Filed Nov. 5, 1937 5 SheeEs-Sheet 4 v nlil? rrn'mr O- m 12 v Fig. 3A. E

//V Vf /V TRS C/MRL Es Saunen FAR/weh, Deceasd Byefrfm Fen/vase Palerme,Execvr/'x y ma a ATTORNEYS oct.4,193. C SFARMER'ETAL 2,131,799

APPARATUS 4FOR EXTRUDING METAL Filed Nov. 5, 1937 5 Sheets-Sheet 5/A/l/E/VTOAJ Cfmz.; San/osu mman, Dewsed q; QE@ 1.1m FRA/less 614mm,einem CHARLES Janes Beane, and

Manns Jnss Fnm'F-w By we, ,M+

Patented Oct. 4, 1938 'UNITED .STATES PATENT OFFICE Garden City. by

Bertha Frances Farmer, ex-

ecutrix, Welwyn Garden City, and Charles James Beaver and 4Thomas JamesFairfield, Bowdon, England, assignors to W. T. Glover and CompanyLimited British companyl Manchester, England, a'

Application November 5, 1937, Serial No. 172,944 In Great'BritainNovember 24, 1936 3 Claims.

This invention relates to that type of apparatus for the extrusion of4metal in which molten metal isfed'into the outer part of a cylindricalcontainer, is allowed to cool there and is then forced by a ram towardsthe inner end of the container, where it passes out in the plastic stateby way of a die or dies. In such apparatus, after the workingvstroke hasbeen completed, the raml is drawn back relative to the container and thefurther charge of moltenmetal is f ed in tol the space between the ramand the remaining part of the previous charge at the inner end of thecontainer. It will be seen that the operation of this apparatus isintermittent and it has been recognized that this kind of operation hasmany disadvantages.

By arranging two or more containers (each with its ram) to deliver intoa single space, which may be spoken of as an extrusion chamber, fromwhich the plastic metal passes into the die and by making the'workingstrokes of the rams at the appropriate time intervals it appearspossible to produce a continuous output from the apparatus.

But in order to do this it is necessary to provide some means to preventthe working stroke of one ram from forcing back metal into a containerfrom which the ram has been withdrawn for the purpose of re-lling thecontainer with molten metal. The metal in the delivery end of eachcontainer, and in the extrusion chamber, and the passages between thisAand these, is in the plastic state. Accordingly, no ordinary mechanicalvalve can be used to prevent` the backward movement of the material.

The present invention supplies an effective means of restraining themetal in the extrusion chamber from being forced back into a containerwhen the pressure therein is reduced so that an effectivemulti-container press of the type indicated can be produced. Inaccordance with the invention the backward movement is restrainedby-providing a particular form of passage between each container and thecommon extrusion chamber, this passage being such that the metal nowseasily from each container into the extrusion chamber, but iseffectively prevented from moving to any substantial extent in `theopposite direction.

It has been found that under the ordinary working conditions of pressureand temperature and rates of movement which are used in extrusionapparatus of the kind indicated, a passage of tapered form offers muchgreater resistance to a flow in one ldirection than in the other. Thecomparatively free direction of flow is that in which the plasticv metalenters at the smaller end of the tapering passage and leaves at thelarger end. The reason for this dilerence in action appears to be thatthe 'end of the passage at which the metal enters acts as a die to fixthe dimensions of the cross-section of the stream of metal. When themetal enters at the smaller end a rod is produced which can move freelythrough the increasing section of the passage. When the direction ofmovement is reversed the rod produced at the larger end stronglyencounters the walls of the passage and is compressed thereby, thusproducing very considerable resistance to flow.

In the further description of the invention, reference will be made tothe accompanying drawings, of these,

yFigures 1 and 2 are curves relating to the proportions of the passage;

Figure 3 is a side elevation with half in section of a press embodyingthe invention;

Figure 4 is a plan view of the central part of Figure 3; and

Figure 5 is an enlarged View in section of the central part' of Figure3.

The effect of the proportions, namely degree of taper, length of passageand area of crosssection, affect very materially the' obtaining of thisautomatic differentiation between directions of flow.

This is shown by the curves in Figures 1 and 2 of the drawings, In thesefigures the vertical scale shows the reduction in the speed of extrusionwhich takes place .when the direction of extrusion is'reversed. Thisreduction is expressed as a percentage of the speed of extrusion whenthe metal is moved from the small to the large end of the taperedpassage. These curves are intended to give primarily indications of theeffects'of the changes of the quantities indicated on the horizontalscales. Their shape is regarded as of greater importance than theprecise values which they indicate. These may be Varied by differentexperimental conditions such as the nature and finish of the surfaces ofthe passages. The general shapes are, however, believed to berepresentative and enable conclusions to be drawn, in such a way as todetermine a satisfactory design of the passage as well as indicating itseffectiveness for the purpose in view. 'I'he curves were obtained byexperiments conducted with passages having dimensions such as arenecessary for metal extrusion presses in current practice.

On the horizontal scale of Figure 1 is measured the taper of thepassage. The passage is circular and the taper is measured as the changeof diameter in mils. for each inch length of the passage (or inhundredths of a millimetre for each'centimetre length). To express it asa percentage it is clear that the gures of the scale should be dividedby ten. It will be seen that as the taper is increased the reduction inextrusion speed rises very rapidly at rst and soon reaches a maximum,and then falls oi much less rapidly. A taper of the order of 3 mils.change of diameter per inch (or 3 hundredthsof a millimetre percentimetre) length of passage gives approximately the maximum result,but the effect is not greatly reduced by a substantial increase oftaper, say, up to 9 mils. (hundredths of a millimetre) change ofdiameter per inch (centimetre) of length.

The horizontal scale of Figure 2 measures the ratio of the length of thepassage to the minimum diameter. It will be seen that the eiect ofincrease of this ratio is great at rst but decreases gradually as thecurve proceeds. It is clear that i the length of the passage shouldalways be substantially greater than its diameter. Values of from 3 to 8times are within practically satisfactory limits, but the higher part ofthe range is preferable.

As a practical example it has been found that 'a passage of circularcross-section, 6 inches (15.24 cm.) in length and with inlet diameter0.750 inch (19.05 mm.) and outlet diameter 0.768 inch (19.51 mm.) willprovide for normal output from the container of ay press of medium sizeand will produce a reduction in the speed of extrusion of 99.4%. That isto say, movement of lead in the reverse direction inthe passage underfull delivery pressure will be restricted to about 0.6% of that in thedirection of free flow under the same pressure, thus effectivelyproducing a nonreturn action.

In Figures 3 to 5 of the drawings is illustrated a two-container pressin which the lead is driven alternately by the two rams into the commonextrusion chamber through tapering passages having proportions such asgiven in the practical example above. 'I'he passages 3 leading from thecontainers 4 to the extrusion chamber 5 are circular in section and havethe diameter at the point 2 measuring 0.750 inch (19.05 mm.) and thediameter at the point I measuring 0.768 inch (19.51 mm.) and thedistance between the points I and 2 measuring 6 inches (15.24 cm).

The ram B for each of the two containers 4 is connected at the rear endto the plunger 1 which works in the hydraulic cylinder 8. Packing pieces23 are provided in the usual manner to i prevent the escape of fluidfrom the hydraulic cylinder 8 and to prevent the movement of fluid pastthe plunger 'I from one compartment to the other Within the cylinder.That part of the surface of the plunger 1 which moves in and out of thecylinder 8 and the interior surface of the cylinder are providedrespectively with a cover 24 and a liner 25 of non-ferrous metal forprotective purposes. These cylinders and the two containers are carriedby side brackets 9 and I0 respectively located by large nuts 26 on twoside rods II which thus hold the parts of the press together. These rodsII are supportedby pedestals I2 which thus carry the weight of thepress.

Between the two containers 4 is held the die box I3 in which are thepassages 3 and the extrusion chamber 5 with the inner die I4 and theouter die I5. The arrangement of dies "shown provides for the extrusionof a tube such as the lcommences its forward stroke.

sheath 2I of .a cable 22. When a cable is being sheathed it is fedupward through the bore of the inner die I4 as shown in Figure 3.

The method of working the pressI so as to obtain a continuous extrusionis as follows. With the right-hand container 4 and ram 6 in thecondition shown in Figure 3, this container is full of metal which hasbeen poured in in the molten state by means of an inclined chute I9, thedelivery end of which is applied to an entry port 28 provided in the endof the container, the

chute being afterwards removed. .The metal in the container has beenallowed to stand until it has sufliciently solidified at the end incontact with the end of the ram 6 to permit this to transmit a steadypressure to the body of metal inthe container. At this point the forwardmovement of the ram 6 is commenced by the admission of water underpressure behind the plunger4 1 through the pipe I6.

At this stage the ram 6 in the left-hand container has reached theinnermost point of its stroke which isv about the position indicated bythe arrow I1 in the right-hand container. As the ram 6 of the right-handcontainer 4 co'mmences to move inward, the ram of the left-handcontainer is withdrawn quickly by the admission of water 'under pressureto the cylinder 8 by way of the pipe I8 so that it acts upon the annularfront face of the plunger 1. This withdrawal of the ram from theleft-hand container leaves the outer part of the container empty, with abody of plastic metal at the inner end of the container and in thepassage 3. When the lefthand ram has been completely withdrawn themolten metal is run into the container, by means of a chute as describedabove, and allowed to cool until the desired solidication near the endof the ram has taken place so that the forward stroke can be commenced.By proper adjustment, of conditions this retraction and relling andpreliminary 'cooling can be made to occupy substantially the time of theworking stroke of the ram in the right-hand container so that the lattermay be withdrawn when the'left-hand ram By a series of alternatingworking strokes in this way the two rams may produce a substantialcontinuous extrusion of metal from the chamber 5 between the dies I4 andI5.

It will be seen that during the extrusion process the metal in thechamber 5 is continuously under the extrusion pressure, and thatmovement of metal into the chamber takes place alternately from theright and left-hand passages 3 (Fig-v ure 5). While one of thesepassages is feeding the chamber the metal in the other passage is at thepoint I subjected to the full extrusion pressure, and this is notresisted within the container since the ram is withdrawn for re-lling atthis stage. It is found, however, that the taper of the passage 3 in themanner indicated suffices to prevent any appreciable backward movementof the metal through the passage into the container.

It will be understood that more than two containers can be used ifdesired and that many ways of grouping the containers in relation toeach other are available. The drawings show by way ofexample only, aconvenient arrangement of a two-container press.

What we claim as our invention is:-

1..An extrusion press for metal, comprising a plurality of containers, asingle extrusion chamber, means for forcing in succession metal fromeach container into the said extrusion chamber 76 and connectingpassages between each container and the extrusion chamber, each passagehaving a small taper and having its larger end near to the extrusionchamber, by reason of which each passage acts as a non-returndevice forthe plastic metal.

2. An extrusion press for metal, comprising a plurality ci containers,a. single extrusion chamber, means for forcing in succession metal fromeach container into the said extrusion chamber and connecting passagesbetween each container and the'extrusion chamber, each passage having asmall taper and having its larger end nearer to the extrusion chamber,by reason of which each passage acts as a non-return device for theplastic metal, the taper, measured as change of diameterin unit lengthof the passage, being between 0.2% and 0.9% of unit length.

3. An extrusion press for metal, comprising a plurality of containers, asingle extrusion chamber, means for forcing in succession metal fromeach container into the said extrusion chamber and connecting passagesbetween each container and the extrusion chamber, each passage having asmall taper and having its larger en'd nearer to the extrusion chamber,by reason of which each passage acts as a non-return device for theplastic metal, the length of 'each passage being from three to eighttimes its diameter.

' BER'I'HA FRANCES FARMER, Ezecutrim of the Estate of Charles SandellFarmer,

Deceased.

CHARLES JAMES BEAVER. THOMAS JAMES FAIRFIELD.

